Friday, November 9, 2012

Preword: The title 'Sandy Repeat' refers to a similar way to how Sandy formed, NOT the strength or effects.

The ECMWF model is printing out a scenario all too familiar for those who went through Superstorm Sandy. Please take a look below.

The ECMWF model is showing a tropical system moving up the waters off the East Coast about 10 days away. Storm systems on this map are defined by oranges and red- the deeper the color, the stronger the storm. As you can see, this storm looks pretty strong. But look out to the west. See that blob of oranges and reds? Yes, that is another storm system. My fear is that these two could phase (combine) into one stronger storm, the same way Superstorm Sandy formed. The reason this is a concern rather than an out to sea forecast is because the strongest vorticity values of this storm are located on the western flank, which means this likely-tropical system is being pulled west.

This is still the ECMWF model, and still for the same time frame. This map now shows 500mb geopotential height, the best level to show high and low pressure systems. High pressure systems are shown by arcing lines, and low pressure systems are shown by depressions in these lines shown above. As you can see, there is a big depression in the East in this image, showing a strong storm system. See the small black circle to the east of North Carolina? That is the same system that I showed you above offshore. Considering that there are only a couple black lines separating these two systems in the image above, I believe that the ECMWF is indicating that these two systems are phasing, just like Sandy.

Now, if this even happens (which there is no for-sure indication it will), it will probably not be as bad as Sandy. Sandy was a Category 1 hurricane just before landfall. This system looks like it would be a Category 1 hurricane at maximum- it will be weaker than Sandy. Also, the ONshore system would likely be weaker than the Arctic one that merged with Sandy, meaning that the possible new, combined system would be weaker than Superstorm Sandy.

However, keep in mind that the ECMWF kept on the right track of Sandy while other models incorrectly took it out to sea. Considering the ECMWF has been showing this Sandy-repeat system for at least two model runs, this is definitely something to watch.

I am not making a call yet, I want to see how the other models react to the ECMWF. Right now, the GFS is not in favor of this solution, so just keep an eye out. This is the wait-and-see mode, not PANIC-RIGHT-NOW mode.

Observed snow cover in Siberia during the month of October is supporting the idea of a back-loaded winter, something many winter weather lovers out there are dreading.

Something forecasters use in the fall months to help predict the upcoming winter is indeed Siberia. In October, the anomaly of snow cover over the region has been proven to correlate with observed Arctic Oscillation anomalies in the following winter. For example, if the month of October held a very below normal snow cover situation for Siberia, the Arctic Oscillation would most likely be on the positive side (warmer weather) for the winter.

If we apply that rule to the observed October 2012 snow cover, here is what I find:

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